In the preparation of liquid treatment compositions, it is an aim to improve technical capabilities thereof and aesthetics. One method of improving the aesthetics of a liquid treatment composition is to make it pearlescent.
Pearlescence can be achieved by incorporation of a pearlescent agent into the liquid treatment composition. Pearlescent agents include inorganic natural substances, such as mica, bismuth oxychloride and titanium dioxide, and organic compounds such as metal salts of higher fatty acids, fatty glycol esters and fatty acid alkanolamides. The present invention relates only to the use of inorganic pearlescent agents. The pearlescent agent can be acquired as a powder, suspension of the agent in a suitable suspending agent or, where the agent is a crystal, it may be produced in situ.
Detergent compositions and pearlescent dispersions comprising pearlescent agent fatty acid glycol ester are disclosed in the following art; U.S. Pat. No. 4,717,501 (to Kao); U.S. Pat. No. 5,017,305 (to Henkel); U.S. Pat. No. 6,210,659 (to Henkel); U.S. Pat. No. 6,835,700 (to Cognis). Liquid treatment compositions containing pearlescent agents are disclosed in U.S. Pat. No. 6,956,017 (to Procter & Gamble). Liquid detergents for washing delicate garments containing pearlescent agent are disclosed in EP 520551 B1 (to Unilever).
The present invention relates to a slurry comprising inorganic pearlescent agent. The slurry described in WO2007/111899 A2 (to Procter & Gamble) uses water as the carrier for pearlescent agent. However, the Applicants have discovered that using water as the carrier for pearlescent agent only allows up to six weeks of physical stability, before the pearlescent agent starts to settle.
The inorganic pearlescent agent slurry of WO2007/11189 is prepared in a batch process. A measured quantity of the inorganic pearlescent agent slurry is then added to the continuous process used to prepare liquid treatment compositions. However, as discussed above, the inorganic pearlescent agents tend to settle from the slurry suspension. This settling causes problems in the continuous processing used to prepare the liquid treatment compositions, since there will be points when there may be too much pearlecence or no pearlecence at all.
One potential solution to these problems may be to increase the viscosity of the slurry. However the end products necessarily have relatively low viscosity, especially at high shear, such that they may be poured or processed. Therefore components of the liquid treatment composition, like the slurry, should not have too high viscosity. Contrarily, if the slurry has low viscosity at low shear, the particulates have a tendency to fall out of suspension and either float or sink upon storage. This results in an undesired, non-homogenous slurry, wherein part of the slurry is pearly and part of it is clear and homogeneous. Such a slurry clearly would have an undesirable effect on the aesthetics of the final composition, which may have too much pearlecence or no pearlecence at all. Hence the Applicant has found that simply varying the viscosity of the slurry, does not adequately solve the problems as set out in the present invention.
Moreover, inorganic pearlescent agents are insoluble and without adequate solution, behave like wet sand, causing problems in processing of the slurry. The wet sand behavior makes the slurry difficult to mix and requires considerable effort from the equipment used in the mixing process.
The present invention provides a slurry and a procedure to prepare the slurry suitable for further processing into a liquid treatment compositions. The present invention specifically relates to improving the physical stability and process lifetime of an inorganic pearlescent agent slurry, and thereby improving the process of preparation and quality of the liquid treatment composition. The present invention also relates to the use of combination of solvent and rheology modifier in a slurry of inorganic pearlescent agents to improve the physical stability and the process lifetime of the slurry. The Applicants have discovered that replacing water by either glycerol or sorbitol solvent increases the physical stability of the slurry, in that the slurry remains physically stable 16 weeks. The present invention also relates to an optimized the process of preparing the inorganic pearlescent agent slurry wherein the addition of inorganic pearlescent agent is strictly controlled.